Ecology of Wisqoq Cave, a raccoon-inhabited cave in Nova Scotia

Moseley et al. Ecology of Wisqoq Cave, a raccoon-inhabited cave in Nova Scotia Max Moseley1, Matt Smith2, Hugh Broders3 & Lynn Burns4 1 PO Box 69, Poskod 10700, GPO Penang, Malaysia [email protected] (corresponding author) 2 371 Avondale Road, Newport Landing, Nova Scotia, Canada [email protected] 3 Department of Biology, Saint Mary’s University, Halifax, Nova Scotia, Canada [email protected] 4 Department of Biology, Dalhousie University, Halifax, Nova Scotia, Canada [email protected] Key Words: gypsum cave, temperature, threshold vegetation, raccoon, bats, guano fauna. Wisqoq Cave is a natural dissolution cave formed in Mississippian age gypsumanhydrite evaporites on the Avon Peninsula, Hants County, Nova Scotia. It is the only biologically pristine cave discovered in Nova Scotia in recent decades and is the only known cave in the Canadian Maritime provinces in which the cavernicolous invertebrate community is dependent on raccoon dung. Description Wisqoq (= Black Ash in the native tongue of the Mi’kmaq people) Cave is located in an area of mature Acadian forest dominated by Eastern Hemlock, White Ash and White Birch. In the immediate vicinity of the cave outcropping gypsum bedrock has eroded into an extremely rugged karst terrain: referred to locally as “plaster land” (Figure 1). In addition to the dominant species the thin soils here support Red and White Spruce, Balsam Fir and an herb and bryophyte understory vegetation. Ferns and various calciphilous mosses also form a cover directly on exposed rock surfaces (Figure 2). The two narrow vertical entrance shafts, P9 and P7.5 are 9 m and 7.5 m in depth respectively. They open into a rather irregular low-ceilinged (≤ 2 m) horizontal chamber (Figure 3) approximately 18 m in length and up to 6 m wide, formed by ceiling breakdown at a depth of about 8–10 m below the present land surface. A standing pond and staining on the walls of the cavern indicate ephemeral or intermittent flooding within the chamber (Figure 3). There are low wet crawlways beneath the chamber and constricted openings here provide access routes into the cave for North American 2013 Speleobiology Notes 5: 66–73 66 Moseley et al. raccoon (Procyon lotor (Linnaeus, 1758)) via deep adjacent sinkholes. The vertical relief from the top of P9 to the lowermost openings is ca. 12 m. Figure 1. Evaporite karst adjacent to the Wisqoq Cave Shaft P9. The shaft is situated at the upper middle of the image, immediately beyond and hidden by the wall of gypsum behind the head of the caver. Photograph by M. Moseley. Figure 2. Shaft P9, Wisqoq Cave. Cushions of pleurocarpous mosses (Hylocomium, Isopterygium and Heterocladium) are present growing near the top of the shaft and on exposed bedrock outside; liverworts and lichens are visible on the walls further down the shaft. Photograph by M. Moseley. 2013 Speleobiology Notes 5: 66–73 67 Moseley et al. Environment Light is visible to the bottom of the shafts, which are threshold-deep threshold zone throughout. There is no ‘deep cave’ environment: most of the cave is in darkness but subject to short-term meteorological effects from the surface and thus transition zone. The air temperature inside the cave was monitored using a data logging temperature sensor (iButton Thermocron, Dallas Semiconductor, Dallas, Texas, USA) deployed at the lower level of the cave from June 2011 until June 2012. The average air temperature inside Wisqoq was 4.9°C (range: -2.9 to 10.6°C). Minor ice was observed inside the cave in February 2011 and January 2013. Air and water temperature spot measurements were made on 26 June 2011 and 20 January 2013 with hand-held thermometers calibrated to 1°C. The June air temperatures showed a gradient from 18°C at the top of shaft P9 to 9°C at the bottom, decreasing to 6°C further inside the chamber. The water temperature of the pond (Figure 3) in the chamber was 4.5°C. In January 2013, when hibernating bats were present in the chamber, the air temperature there was 5.5°C. Figure 3. Chamber in Wisqoq Cave. Brown-colored mud and staining on the rocks and walls indicate former water levels: the pond in the center of the picture is semipermanent. Festoons of plant roots growing through the ceiling are visible at the upper right. Photograph by M. Moseley. Environmentally-stable ‘deep cave’ habitats hardly occur in the small caves known in Nova Scotia, but can be expected in more extensive mineworkings (Table 1). Average monthly temperatures in the adit of Centre Rawdon Gold Mine vary only ca. 1°C annually. In the dark zone of Frenchman’s Cave, considered a fairly typical local cave (Moseley 2007), the annual variation is ca. 4°C. It can be significantly more, for example conservatively ca. 7–8°C in Cave of Bats (measured over only 8 winter months), but the 2013 Speleobiology Notes 5: 66–73 68 Moseley et al. annual range of nearly 14°C in Wisqoq Cave is unusually large. The anomalous temperature variation recorded in Wisqoq can be explained by a seasonal and bidirectional ventilation pattern resulting from a vertical height difference of ca. 12 m from the lowest egress points to the top of the shafts, and changing inside-outside temperature differentials. The spot temperature readings made in June 2011 are consistent with slow movement of warm air down the shafts replacing heavier colder cave air which egresses via the lower level openings. In winter, as the outside temperature falls below that inside the cave the direction of flow reverses. At this time warmer air rising up the shafts draws in cold air from outside, resulting in midwinter in sub-freezing air temperatures in the lowest passages. Table 1. Representative dark zone (dz) temperatures (°C) recorded in caves and mines in central Nova Scotia. Unpublished data (iButton Thermocron) except Frenchman’s Cave after Moseley (2007). Site Codes follow Moseley (2007). Site County Site Dates Code SC Jun 2011Jun 2012 CRM Dec 2009Nov 2010 Mean Temp (°C) 4.9 Temp Range (°C) -2.9–10.6 Wisqoq Cave (lower level), Avondale Centre Rawdon Gold Mine (108 m from adit entrance) Hayes Cave (75 m from the entrance), South Maitland Frenchman's Cave (dz), St Croix Minasville Ice Cave, (1st chamber, dz), Minasville Cave of Bats, (dz), Dutch Settlement Hants 7.1 6.6–7.6 Hants HG 5.7 4.2–6.8 Hants FC 5.8 3.8–7.6 Hants MIC Dec 2011Nov 2012 4.4 2.1–6.6 Halifax CB Oct 2009May 2010 5.3 2.6–10.2 Hants Apr 2004Nov 2005 Biology Although there is a rich fern flora in the immediate vicinity, plant zonation within the vertical entrance shafts themselves is truncated, being restricted to bryophytes and lichens with no outermost ‘fern zone’ (Figure 2). Three species of pleurocarpous moss (Hylocomium brevirostre (Bridel) Schimper, Isopterygium muellerianum (Schimper) Jaeger, and Heterocladium dimorphum (Bridel) Schimper), two liverworts (Calypogeia sp. and Lophocolea sp.) and a crustose lichen (Lepraria sp.) grow on the sides of the upper parts of the shafts. All six are plants typical of base rich substrates in Nova Scotia, and none of the rarer calciphilous bryophytes and lichens known to occur on gypsum karst in the province (Anderson and Neily 2010) were collected. 2013 Speleobiology Notes 5: 66–73 69 Moseley et al. The most prominent bryophyte at this site, the moss I. muellerianum, is present from the shallow threshold to the deepest extent of green vegetation. This is a common moss widely distributed in North America, Europe and Asia growing on cliffs, rocky outcrops and boulders in forests (Rohrer 1999). Another common species H. brevirostre is only present in the uppermost part of the shafts i.e. the shallow threshold. This moss is normally found on soil, humus, rotten logs and rocks in moist forests. It occurs in the British Isles and elsewhere in Western Europe, as well as in eastern North America and there are records from Costa Rica, Guatemala and Japan (Rohrer 1999). It appears therefore to be of European origin, introduced and now established elsewhere including in the Canadian Maritime provinces. Species of the sterile leprose lichen Lepraria are common in cave thresholds in Britain and other countries (Pentecost and Zhang 2004). Plant roots penetrate in places through the cave ceiling (Figure 3), but no fauna was found on them. No aquatic fauna was found in the standing pool. There is also little evidence of the usual dipteran and other parietal fauna characteristic of local caves (Moseley 2007) although the spider Meta ovalis (Gertsch, 1933) is present throughout the cave from the outermost threshold ‘moss zone’ into the dark zone. This spider is widespread in caves, mine adits, damp cellars and similar places throughout the province (Moseley 2007), but its occurrence on green vegetation just inside the entrances at Wisqoq is unusual: adults and the distinctive egg sacs, attached to moss, were observed in both entrance shafts. Previous inventories of caves in mainland Nova Scotia and New Brunswick have shown that porcupine scat is the most important food source in cave habitats in this geographical region (Moseley 2007). In contrast the invertebrate biota in Wisqoq Cave is associated with inputs of dung of raccoon. Evidence of foraging and denning by raccoons has been seen in some local caves (Moseley 2007; McAlpine et al. 2011) and there is a recent report of opportunistic scavenging of dead and diseased bats (McAlpine et al. 2011) but no previous description of raccoon feces-based ecology in any cave in the region. Skeletal remains, scat, latrines, grooming pellets, tracks and visual sightings show that the cave is used year-round by raccoons as a den. Partly-decomposed feces (i.e., retaining their shape) sampled in June 2011 supported populations of leiodid beetles (Prionochaeta opaca Say, 1825: adults and larvae), ptiliid beetles (Acrotrichis castanea Matthews, 1877), millipedes (Cylindroiulus latestriatus (Curtis, 1845)), larvae of the fly Trichocera maculipennis (Meigen, 1818), unidentified Acari and isotomid Collembola. The raccoon probably uses caves throughout its range. Raccoon scat cave communities are reported, for example, from Kentucky (Poulson 1992) and Indiana (Lewis 2002). Fresh dung is a high-energy food source that undergoes rapid successional breakdown (Poulson 1992). In Mammoth Cave, Kentucky (Poulson 1992) and Hoosier National Forest in Indiana (Lewis 2002), the initial utilization of moist feces 2013 Speleobiology Notes 5: 66–73 70 Moseley et al. is usually by dipteran larvae such as Leptocera, Amoebalaria and Spelobia. These attract Quedius spelaeus and other staphylinid beetle predators. Collembola and Acari are rarer, smaller in size and feed on the low energy components remaining after the early succession detritivores have left. In Indiana several obligate subterranean species typically appear including Sinella cavernarum and S. alata (Collembola), Pseudotremia salisae (Diplopoda) and Phanetta subterranean (Araneae). In Wisqoq the two important detritivores are T. maculipennis maggots and C. latestriatus. These can be present in considerable numbers on raccoon feces early in the ecological succession. Both C. latestriatus and another millipede Polydesmus angustus Latzel, 1884 that was also collected in the cave are introduced European species. They are found associated with porcupine dung in Frenchman’s Cave (Moseley 2007) so it appears that both are now well established in local cave communities. There is an unusually high number of introduced European invertebrate species in Nova Scotia caves (Moseley 2007). The presence of large populations of millipedes is reminiscent of guano-rich tropical caves. The native North American beetle A. castanea occurs in abundance in porcupine dung piles in Frenchman’s Cave (Moseley 2007) so, as in the case of the millipedes, its presence at this second site points to it being a bona fide ‘cave’ inhabitant. Although there is only one other known North American cave record (Sörensson 2003) of this species it seems likely that these tiny beetles are present in many caves but overlooked due to their diminutive size and obscure habits. Another native beetle, the widely distributed species P. opaca is primarily found associated with carrion in forested environments, but also on bat guano in caves in the southeastern United States (Peck 1977). There are records from 52 caves in 12 states in the southeastern United States west to Arkansas, Oklahoma, Missouri, and Iowa (Peck 1997; Peck and Cook 2002). It is also present in caves in the northern part of its range in Ontario (Peck 1988) and Nova Scotia (current report) suggesting that it is cavernicolous throughout its range where a suitable substrate is available. Its notable absence (Moseley 2009) from previous cave collections in our region might mean that it cannot live on porcupine scat. The absence of carabids is consistent with previous observations in caves in Nova Scotia (Moseley 2009). An adult female Wadotes calcaratus (Keyserling, 1887) (Araneae: Amaurobiidae) was collected. This widely distributed and fairly common native funnel-web spider has been reported as a trogloxene (or accidental) of caves in southern Ontario, Alabama, Georgia, and Tennessee (J. Roth, personal communication). The new record from Nova Scotia suggests that it might actually be found in suitable caves throughout its range; possibly more regularly than implied by the term ‘trogloxene’. Other invertebrates collected from the dark zone of the cave were Aporrectodea tuberculata (Eisen, 1874) (Oligochaeta: Lumbricidae) and a roundback slug (Arion probably subfuscus) (Gastropoda: Arionidae). These and other earthworms and slugs are sometimes 2013 Speleobiology Notes 5: 66–73 71 Moseley et al. recorded in local caves, and are further examples of European introductions that have actively colonized caves in Nova Scotia (Moseley 2007). Eight hibernating bats were counted in January 2012 and six in January 2013. In order to avoid disturbance they were not closely inspected but at least one was a tricolored bat (Perimyotis subflavus (F. Cuvier, 1832)). Much of the cave chamber is unsuitable for bats because the low ceiling facilitates raccoon predation: the few bats present roost in the higher and less reachable pockets in the ceiling. Low winter temperatures and occasional flooding might be further negative factors limiting the suitability of parts of the cave. A single healthy-looking Red Eft – the terrestrial phase of the Eastern Newt (Notophthlamus viridescens Rafinesque, 1820) (Amphibia: Salamandridae) – was collected inside the cave on 29 May 2011. This is the first cave-associated record of this newt in Atlantic Canada. Because of its unusual and relatively undisturbed ecology Wisqoq Cave is being treated informally as a nature reserve: the exact location is not being publicly disclosed and access is restricted. It is however within the footprint of a proposed new opencast gypsum mine and at risk of destruction. Acknowledgements Special thanks are due to J. Guy for particularly valuable help in the field. Cave exploration, mapping and bat count support were assisted by D. Archibald, K. Greer, D. Munroe, P. Pautel and D. Sawatzky. Devan Archibald and two anonymous reviewers also kindly read and made useful suggestions for improvement of the draft. The following systematists are thanked for identifying specimens: D. Davies (Gastropoda), C. Ewing (Araneae), J. Gilhen (Amphibia), C. Majka (Leiodidae), T. Neily (bryophytes and lichens) and M. Sörensson (Ptiliidae). Thanks are also due to the staff of the Nova Scotia Museum, especially A. Hebda, M. Munroe and C. McCorry. Literature Cited Anderson, F., & Neily, T. 2010. A reconnaissance level survey of calciphilous lichens in selected karst topography in Nova Scotia with notes on incidental bryophytes. 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